Pulse Thump in the Cummins - Dodge Cummins Diesel Forum
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post #1 of 71 (permalink) Old 10-21-2017, 02:48 AM Thread Starter
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Pulse Thump in the Cummins

Any idea what is causing this? I think this there has been a hint of of this "thump - irregular heart beat" back 20k miles ago (108k now), but in the last 4k miles or maybe the last time i pulled the fiver I really noticed it and so other than a demo of the issue tried to take it really easy on the throttle, it has accentuated greatly on that trip.

I really notice it under a load, but can even notice it unloaded and going up a very slight hill now.

Video of pulling 15K up a grade - very noticeable: https://youtu.be/zJhy56HRs6g


I've checked valves found what i had previously adjusted to 0.018 / .009" lash - two valves were at .0115 (.0025 lash increase)

Cylinder / Int / Exh

#1 / .008 / .018
#2 / .008 / .017
#3 / .009 / .018
#4 / .0115 / .019
#5 / .011 / .018
#6 / .008 / .0185

All are adjusted back to .018/.009 and the following videos are at that condition.



Cracked injector lines to all cylinders - completely noticeable when a cylinder drops.

See if you can hear the pulse.

https://youtu.be/mdMdJWoBd04

https://youtu.be/r-Rq5AVzbeE


Not sure where to go nextto pinpoint the cause of this. Need the folks with the experience and knowledge to help diagnose.

Thx


1995 3500 2WD NV4500 105k Mods: stock plate full fwd + 0.060", AFC full fwd, stock gov springs +3 clicks, BD exh. brake, 60lb springs, EGT/Boost gages, rear axle air bags, 20psi boost (max) Towing: Alpenlite Avalon 36' ~14k, Reese 18K dual pivot hitch
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post #2 of 71 (permalink) Old 10-21-2017, 11:56 AM
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"This video is unavailable"

All three links.
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post #3 of 71 (permalink) Old 10-21-2017, 04:36 PM Thread Starter
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Sorry about that - i believe i have fixed them now - should be able to play.

Thx.

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1995 3500 2WD NV4500 105k Mods: stock plate full fwd + 0.060", AFC full fwd, stock gov springs +3 clicks, BD exh. brake, 60lb springs, EGT/Boost gages, rear axle air bags, 20psi boost (max) Towing: Alpenlite Avalon 36' ~14k, Reese 18K dual pivot hitch
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post #4 of 71 (permalink) Old 10-21-2017, 04:54 PM
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I could hear it in video #3. Pour cold water on the injection pump while it's doing it and if it clears up, there's your problem.

'97 3500 4x4 CC DRW, 4.10, Banks PP, BD tc, vb, eb, 60# springs, Torqloc, gauges, Weatherguard, B&W...
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post #5 of 71 (permalink) Old 10-21-2017, 08:26 PM Thread Starter
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Quote:
Originally Posted by brownbear View Post
I could hear it in video #3. Pour cold water on the injection pump while it's doing it and if it clears up, there's your problem.
Started with engine cold with water hose running over injection pump. No change. I took this immediately to 1000 to 1200 rpm and you can really feel/hear the thumpy pusating vibration there.

Video here: https://youtu.be/iCyGO_kUP2s

So not a positive signal from this experiment.

How about injector pop pressure - would these symptoms stongly point to that? I may just buy a pop tester and see how they fair.

1995 3500 2WD NV4500 105k Mods: stock plate full fwd + 0.060", AFC full fwd, stock gov springs +3 clicks, BD exh. brake, 60lb springs, EGT/Boost gages, rear axle air bags, 20psi boost (max) Towing: Alpenlite Avalon 36' ~14k, Reese 18K dual pivot hitch
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post #6 of 71 (permalink) Old 10-21-2017, 08:36 PM
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You'll want the engine hot for the cold water test but it's not the end all/be all of on engine pump test.

I would verify fuel pressure before you start anywhere else.
Stock should see 15-20psi at idle and 25-30psi at 2000rpm

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post #7 of 71 (permalink) Old 10-21-2017, 09:55 PM Thread Starter
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Quote:
Originally Posted by hemirunner426 View Post
You'll want the engine hot for the cold water test but it's not the end all/be all of on engine pump test.

I would verify fuel pressure before you start anywhere else.
Stock should see 15-20psi at idle and 25-30psi at 2000rpm

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WRT fuel pressure, just did the fuel system 2k miles ago, (new Cummins lift pump, hoses, filters, pre-heater delete, OFV (torque tek) about 2000 miles ago - pressure was about 22-24psi at 2000 RPM.

I could check it again but i doubt anything has changed and this thump was at least slightly there prior to fuel system refresh. The refresh made zero impact on the way the truck ran. I did that because of age (incidently I did find the outflow port check valve was grenaded in the OEM lift pump at 104K miles, surprising), however it didn't appear to effect anything (think it relied on the piston check valve to prevent back flow).

Ok i'll check it to verify and make sure i'm not chasing the tail. Good idea.

1995 3500 2WD NV4500 105k Mods: stock plate full fwd + 0.060", AFC full fwd, stock gov springs +3 clicks, BD exh. brake, 60lb springs, EGT/Boost gages, rear axle air bags, 20psi boost (max) Towing: Alpenlite Avalon 36' ~14k, Reese 18K dual pivot hitch
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post #8 of 71 (permalink) Old 10-21-2017, 11:44 PM
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The local Bosch service center will pop test stock injectors for free. Perhaps the local one to you will do the same.

97 3500, 2 WD, G56, slightly bombed, 1.3 million miles. Started the second million on 8/24/13
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post #9 of 71 (permalink) Old 10-28-2017, 11:49 PM Thread Starter
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Pulled injectors - will take to Bosch dealer Monday - they will pop test as courtesy, I wonder it that allows them to see spray pattern?

Fuel pressure is 24 psi @750rpm and 21-22 psi at 2000 rpm.

Injectors shown just as pulled w/o handling them. I suppose the body's aer wet on some due to the cracked rubber seals on the injector hold down nut.

The tips look different among them - some "dry clear of residue" some black-ish with residue. Typical, or any indication here of combustion differences?

Should i do a compression check while these are out or - "head in the sand" ingnorance is bliss?
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1995 3500 2WD NV4500 105k Mods: stock plate full fwd + 0.060", AFC full fwd, stock gov springs +3 clicks, BD exh. brake, 60lb springs, EGT/Boost gages, rear axle air bags, 20psi boost (max) Towing: Alpenlite Avalon 36' ~14k, Reese 18K dual pivot hitch
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post #10 of 71 (permalink) Old 10-29-2017, 12:14 PM
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Visual inspection from pictures is a bit difficult.
However, they appear to be normal. Soot differences between the injectors is not something to be too concerned about. What matters is when they pop and the quality of the spray pattern.

Your fuel pressures are a bit suspect. This was done with no load, correct? Fuel pressure should rise as RPM rise.
Can you get some readings driving the truck?

Never did ask what year this truck is. Do you know if it's a 160HP pump?

91.0 D250 A727 w/ 216k on the clock. i/p replaced 20k ago, lift pump 2k, 1 turn fuel, 2 turns smoke, ground & polished AFC pin, timing bump, 366 spring 94 2500 4x4, 49k miles, Farrell Diesel rebuilt 215 pump, PDD 5x12 SAC, SXE 362, built 47RH
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post #11 of 71 (permalink) Old 10-29-2017, 08:12 PM
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Quote:
Originally Posted by PGWIN View Post
Should i do a compression check while these are out or - "head in the sand" ingnorance is bliss?
You should also scope the cylinders while the injectors are out.

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post #12 of 71 (permalink) Old 10-29-2017, 09:10 PM
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The rubber seals are dust seals only. The wetness from fuel has nothing to do with them, other than what have might have dripped from the supply lines.

97 3500, 2 WD, G56, slightly bombed, 1.3 million miles. Started the second million on 8/24/13
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